ci: replace mkdocs-pr.yml with path-gated notebook-executing variant

[jonathanhhb]

Before: two PR-time docs builds, both with mkdocs-jupyter execute=false.

• github-actions.yml's "docs" matrix entry (tox -e docs → mkdocs build)
• mkdocs-pr.yml ("MkDocs Build on PR" → mkdocs build) Neither caught a broken notebook because the static mkdocs-jupyter render doesn't actually run the cells; notebooks were only executed at manual release time (release-publish.yml's docs-deploy job via mkdocs.ci.yml).

After:

• github-actions.yml's "docs" matrix entry stays as-is — fast, runs on every PR, catches mkdocs config breakage.
• mkdocs-pr.yml is deleted (it was duplicate work).
• New mkdocs-pr-notebooks.yml runs mkdocs build --config-file mkdocs.ci.yml (mkdocs-jupyter execute=true, allow_errors=false), gated to PRs that touch:
  • docs/tutorials/notebooks/** — notebooks themselves
  • mkdocs.ci.yml / mkdocs.yml — config that affects execution
  • docs/requirements.txt — runtime deps
  • pyproject.toml — laser-generic deps/version
  • src/** — package code notebooks import
  • the workflow itself — so editing it self-tests

Cost: PRs that touch any of those paths pay the notebook-execution runtime (currently ~15 min total, dominated by nb 06's ~8 min sim); PRs that touch only unrelated code (sphinx, tests, other CI, README) skip the heavy job entirely.

timeout-minutes: 30 leaves headroom; bump when longer notebooks land.

[Copilot]

Pull request overview

Replaces the duplicate, non-executing PR docs build (mkdocs-pr.yml) with a path-gated workflow (mkdocs-pr-notebooks.yml) that actually executes notebooks via mkdocs.ci.yml, so broken tutorial notebooks are caught at PR time instead of only at release.

Changes:

• Delete mkdocs-pr.yml (it duplicated the fast docs build already in github-actions.yml and never executed notebooks).
• Add mkdocs-pr-notebooks.yml that runs mkdocs build --config-file mkdocs.ci.yml with execute: true, gated to paths that can affect notebook execution.
• Set timeout-minutes: 30 to accommodate the current ~15 min notebook execution runtime.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
.github/workflows/mkdocs-pr.yml	Removes the redundant non-executing PR docs build.
.github/workflows/mkdocs-pr-notebooks.yml	New path-gated workflow that builds docs with notebook execution enabled.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[jonathanhhb]

Build failure will be fixed with #188.